1. Field of the Invention
The present invention relates to a fusing apparatus and an image forming apparatus.
2. Description of Related Art
Conventionally, there is a fusing apparatus which heats and applies pressure while nipping a sheet on which a toner image is formed to fuse a toner image which is not yet fused on the sheet. In such fusing apparatus, the sheet nipped by the fusing apparatus may stick to the fusing apparatus after fusing. As described in, for example, Japanese Patent Application Laid-Open Publication No. H3-164777, there is a fusing apparatus including an air blasting apparatus which sends an airflow between the sheet and the fusing apparatus to separate the sheet from the fusing apparatus. Such blasting apparatus is provided to be able to separate from the fusing apparatus a sheet with the largest size in the width direction orthogonal to the conveying direction of the sheet among the sheet used in image forming. In other words, the range of air blasting of the air blasting apparatus corresponds to the sheet with the largest size in the width direction.
However, the conventional air blasting apparatus blasts air in a range corresponding to the sheet with the largest size in the width direction regardless of the size in the width direction of the sheet orthogonal to the conveying direction of the sheet. Therefore, air is blasted to a range unnecessary for separating the sheet, and needless energy is consumed.
When an image is formed on a sheet with a size in the width direction smaller than the sheet with the largest size in the width direction, the portion of the fusing apparatus positioned outside the edge section of the sheet in the width direction is cooled by directly receiving all of the air from the air blasting apparatus. Therefore, after an image is formed on a sheet with a size in the width direction smaller than the sheet with the largest size in the width direction, when an image is formed on a sheet with a larger size in the width direction, the cooled portion of the fusing apparatus is used to form the image and the fusing apparatus needs to be heated again before fusing processing starts. In other words, blasting air in a range unnecessary for separating the sheet unnecessarily cools the fusing apparatus and the fusing apparatus needs to be heated again. Therefore, the energy efficiency becomes even worse.